(1) Field of the Invention
The present invention relates to a production of a point assembly for a ball-point pen in which a ball as a writing element is loosely held with some play and kept from slipping out with a properly sized gap which establishes a flow passage of ink, and further relates to improvement of a ball-point pen using a point assembly thereof.
(2) Description of the Prior Art
In conventional writing implements, ink evaporation occurring when the implement is not used for a long time is prevented by fitting a cap. Further, there are ball-point pens and small-tube type writing implements having a cap with a sealing element therein which is composed of elastic rubber, etc., and seals the pen point in order to prevent ink starvation or so-called forward leakage (ink drip from the pen point), which would occur due to drawing of air through the pen point when the pen is impacted by being dropped. However, in the case of a retractable or clicking type ball-point pen as well as in the case where the user has forgotten to fit the cap, in the case of a writing implement where the ink used is unavoidably volatile, and in other cases, ink starvation and air drawing tend to occur, and in the worst case the writing implement itself may accidentally become disabled. Countermeasures against such cases, include: inhibiting ink evaporation as much as possible by creating the point assembly of the ball-point pen of metal; increasing the viscosity of ink (up to 5,000 cp to 10,000 cp); increasing the content of non-volatile solvent; decreasing the out-flow of ink by narrowing the ink flow channel in the point assembly; and creating interior pressure within the barrel interior equal to or higher than the pressure of the surrounding air to cause the interior ink to flow out. In particular, these problems have not been resolved for so-called intermediate type ball-point pens which use ink of a medium viscosity and present intermediate properties between oily and aqueous ball-point pens. Although ball-point pens of this type have such imperfection, they have been put onto the market because of other merits.
In conventional ball-point pens, the problems of dry-up due to forward leakage, air drawing, evaporation or the like, are primarily solved by pressurizing the ink or the barrel interior, or by other appropriate mechanisms. Even if such a means is not provided, the point assembly is protected with a hermetic cap or by providing an elastic material such as rubber etc., in close contact with the tip of the point assembly. In the above cases, rather complicated mechanisms are needed, thus causing increased occurrence of accidents due to the imperfection of such mechanisms, or if the mechanism works well, it costs more increasing the price of the ball-point pen. For those in which the defects are offset by a cap only, it cannot provide an effective solution, for it has a further problem in that the performance cannot be maintained unless the user often puts the cap in place. For those in which the defects are solved by ink, this settlement is achieved by sacrificing the writing performances, such as drying performance of ink (i.e., ink not being likely to be dry after the drawing of lines) and writing sensation. To make matters worse, the ball seat in the point assembly will be worn out due to reduced smoothness of ink, so that the ink flow increases with use, and in the worst case, writing itself becomes impossible.